This invention relates to electric rotating machines and more particularly to unidirectional synchronous and stepper motors.
The present invention, while of general application, is particularly well suited for use in frictional horse power motors. Certain illustrative motors of this general class are disclosed in Arthur W. Haydon U.S. Pat. Nos. 3,909,646 granted Sept. 30, 1975; 3,495,113 granted Feb. 10, 1970; 3,495,111 also granted Feb. 10, 1970 and 3,564,214 granted Feb. 16, 1971; and Arthur W. Haydon and John J. Dean U.S. Pat. No. 3,770,998 granted Nov. 6, 1973.
One problem which has existed in the design of electric motors and other electric rotating machines, including those of the foregoing type, was the added manufacturing cost and complexity resulting from the need for providing shading rings of other ancillary devices to insure that the rotor of the motor uniformly and consistently began rotating in a prescribed direction upon energization of the field coil. Previous attempts to simplify the design by eliminating such shading devices resulted in a motor that either did not have a unidirectional starting characteristic or necessitated a mechanical ratchet mechanism (called a "no-back" device) in order to prevent the rotor from rotating in the wrong direction. The design of prior unidirectional motors, already overly complex, was further complicated in various other respects, and the motors included an unnecessarily large number of component parts which were difficult and expensive to manufacture and assemble.